package icom.acm.filter;

import java.io.IOException;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;

public class SetCharacterEncodingFilter implements Filter {

    // 编码的字符串
    protected String encoding = null;

   // 过滤器的配置
    protected FilterConfig filterConfig = null;

   // 是否忽略客户端的编码
    protected boolean ignore = true;

   // 销毁过滤器
    @Override
	public void destroy() {

        this.encoding = null;
        this.filterConfig = null;

    }

   // 过滤方法
    @Override
	public void doFilter(ServletRequest request, ServletResponse response,
                         FilterChain chain)
          throws IOException, ServletException {

        // 如果使用过滤器，忽略客户端的编码，那么使用通过过滤器设定编码
        if (ignore || (request.getCharacterEncoding() == null)) {
            String encoding = selectEncoding(request);
            if (encoding != null)
                request.setCharacterEncoding(encoding);
        }

        // 传送给下一个过滤器
        chain.doFilter(request, response);

    }


    // 初始化过滤器
    @Override
	public void init(FilterConfig filterConfig) throws ServletException {

        this.filterConfig = filterConfig;
        this.encoding = filterConfig.getInitParameter("encoding");
        String value = filterConfig.getInitParameter("ignore");
        if (value == null)
            this.ignore = true;
        else if (value.equalsIgnoreCase("true"))
            this.ignore = true;
        else if (value.equalsIgnoreCase("yes"))
            this.ignore = true;
        else
            this.ignore = false;

    }

    // 返回过滤器设定的编码
    protected String selectEncoding(ServletRequest request) {

        return (this.encoding);

    }
}